A capacitor used around a CPU (central Processing Unit) in a personal computer or the like is required to have a high capacitance and a low ESR value so that voltage fluctuation can be suppressed and heat generation can be reduced when a high ripple current is passed.
Generally, two or more of aluminum solid electrolytic capacitor and tantalum solid electrolytic capacitor are used.
Such a solid electrolytic capacitor is constituted by one electrode (conductor) consisting of aluminum foil having micropores in its surface layer or a sintered body of tantalum powder having fine pores inside, a dielectric layer formed on the electrode surface and the other electrode provided on the dielectric layer (generally, a semiconductor layer).
Examples of method for forming a semiconductor layer which is to serve as the other electrode in a capacitor include methods of forming the layer by applying a current as described in Japanese Patent No. 1868722 (Patent Document 1), Japanese Patent No. 1985056 (Patent Document 2) and Japanese Patent No. 2054506 (Patent Document 3). In each of the methods, a conductor having a dielectric layer formed thereon is immersed in a solution for forming a semiconductor layer and then a voltage is applied (a current is applied) between the conductor serving as an anode and an external electrode (cathode) provided in the solution for forming a semiconductor layer, to thereby form a semiconductor layer.                [Patent Document1]Japanese Patent No. 1868722        [Patent Document2]Japanese Patent No. 1985056        [Patent Document3]Japanese Patent No. 2054506        